The present disclosure relates to a display device, and more particularly, to a display device with an integrated touch screen.
A related art display device is described with reference to FIGS. 1 to 3.
FIG. 1 is a sectional view of one pixel area of a related art display device. FIGS. 2 and 3 are varied views of portion B of FIG. 1. The related art display device as illustrated in FIG. 1, includes a substrate 100, a thin film transistor that is a switching element, a first protective layer 134, a second protective layer 140, a pixel electrode 151, a connection line 161, a third protective layer 170, and a common electrode 181.
The thin film transistor is formed in a unit pixel area, and includes a gate electrode 110, a gate insulation layer 120, an active layer 130, a source electrode 131, a drain electrode 132, and an etch stopper 133.
The first protective layer 134 and the second protective layer 140 are formed on the thin film transistor, and particularly, the second protective layer 140 is formed of photo acryl.
The pixel electrode 151 is used as an electrode for display driving and is connected to the drain electrode 132 of the thin film transistor through a contact hole 141 that is formed in the second protective layer 140.
The connection line 161 (e.g. formed of metal) is on the second protective layer 140. The connection line 161, for example, applies a display driving signal or a touch driving signal to the common electrode 181. The third protective layer 170 is formed on the connection line 161, the pixel electrode 151, and the second protective layer 140.
The common electrode 181 and the pixel electrode 151 are formed on different layers. In a display driving mode of a display device with an integrated touch screen, the common electrode 181 generates an electric field together with the pixel electrode 151 and is thereby used as an electrode for display driving. In a touch driving mode of a display device with an integrated touch screen, the common electrode 181 is used as a touch electrode for sensing a touch.
On the other hand, as illustrated in a portion A of FIG. 1, when the connection line 161 of metal is deposited on the second protective layer 140 of photo acryl, due to an adhesive failure between metal and photo acryl, a peeling problem can occur in a subsequent process after deposition, and thus, there is a possibility that the connection line 161 will be damaged.
Even though the connection line 161 is not damaged due to the peeling problem, when a peeling problem occurs in a boundary portion of an adhesive surface, the boundary portion of the adhesive surface can be contaminated by an etching solution and a stripping solution in an etching process and a stripping process. For this reason, additional cost and time are expended to remove the contamination.
To solve the peeling problem, a buffer passivation layer can be formed between the second protective layer 140 and the connection line 161. In this case, however, cost and time are expended by such an additional process.
Moreover, as illustrated in FIGS. 2 and 3, in forming the contact hole 141 for connecting the pixel electrode 151 and the drain electrode 132, when the step height of the contact hole 141 is large or an error, such as a reverse taper, occurs in the first protective layer 134, the disconnection of the pixel electrode 151 can occur in a connection portion connected to the drain electrode 132, and the disconnected portion is exposed by the etching solution and the stripping solution, causing the damage of the drain electrode 132.
Some limitations of the related art display device are described below.
First, a peeling problem can occur due to an adhesive failure between the second protective layer of photo acryl and the connection line of metal, resulting in damaging the connection line and/or contaminating the boundary portion of the adhesive surface.
Second, when the buffer passivation layer is formed for solving the peeling problem between photo acryl and metal, cost and time are expended by an additional process.
Third, when the step height of the contact hole for connecting the pixel electrode and the drain electrode is large or when a reverse taper occurs in the first protective layer, the pixel electrode can be disconnected, and the drain electrode in the disconnected portion is damaged by the etching solution and the stripping solution.